Liquid crystal display devices utilize a liquid crystal composition for display. The typical display mode thereof is irradiating a liquid crystal display panel containing a liquid crystal composition sealed between paired substrates with backlight illumination and applying voltage to the liquid crystal composition to change the alignment of the liquid crystal molecules, thereby controlling the amount of light passing through the liquid crystal display panel. Such liquid crystal display devices have features including a thin profile, light weight, and low power consumption, and have therefore been used for electronic devices such as televisions, smartphones, tablet terminals, and car navigation systems.
In a liquid crystal display device, the alignment of liquid crystal molecules with no voltage applied is typically controlled by alignment films having been subjected to an alignment treatment. The alignment treatment has conventionally been performed by the rubbing method of rubbing the surface of an alignment film with a roller or the like. However, since the number of the conductive lines and the area of the black matrix provided in the liquid crystal panel have been increased, irregularities are now more likely to occur on the substrate surfaces in the liquid crystal panel. With irregularities on the substrate surfaces, the portions near the irregularities may not be properly rubbed by the rubbing method.
In order to deal with this problem, studies and development have been made on a photo-alignment method which is an alternative alignment treatment method to the rubbing method and irradiates the surface of an alignment film with light. With the photo-alignment method, an alignment treatment can be performed without contact with the surface of the alignment film. The photo-alignment method therefore has an advantage that alignment treatment is less likely to be uneven even with irregularities on a substrate surface, so that a favorable liquid crystal alignment can be achieved on the entire substrate.
As a liquid crystal display device having an alignment film, for example, Patent Literature 1 discloses a liquid crystal panel having a liquid crystal layer, an electrode, an inorganic material film, and an alignment film containing a light stabilizer mainly composed of a hindered amine compound.